krysor that is likely your problem in that case. Turning off internet connectivity checks also prevents the OS from handling captive portals.
https://grapheneos.org/faq#default-connections
GrapheneOS also adds the ability to fully turn Off the connectivity checks. This results in the OS no longer handling captive portals itself, not falling back to other networks when some don't have internet access and not being able to delay scheduled jobs depending on internet access until it becomes available.
I think the screen for internet connectivity check could probably be updated to include a mention of this, because otherwise the only way you can know that turning them off breaks captive portals is to find it buried in the middle of the FAQ, or if you happen to have read about it before.